1. Field of the Invention
The present invention relates to an improvement of an X-ray diagnostic apparatus of pre-ignition type.
2. Prior Art
The X-ray diagnostic apparatus of the pre-ignition type has been developed for enabling irradiation of stabilized intensity and for preventing delay in the rise of the tube current at the time of start of X-ray irradiation as well as for preventing over-shooting by heating the filament of the X-ray tube prior to impressing a source voltage between the anode and cathode of the X-ray tube.
This kind of X-ray diagnostic apparatus for pre-ignition type always need stable rise of the X-ray regardless of fluctuations in the source voltage. To meet this need, the electric power is supplied from a DC power source through an inverter to the primary winding of the filament transformer, and also from another DC power source through another inverter to the primary winding of the high-voltage transformer of the high-voltage generating circuit of a conventional apparatus, to thereby prevent fluctuations in the power supply to the primary windings of the transformers.
For instance, an apparatus for effectively preventing another problem of the X-ray diagnostic apparatus of the pre-ignition type, that is, overshoot which is apt to be generated during the rise of the tube current, has been disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 57-13700 by the present inventor. In this invention, a DC stabilized power source circuit and inverter are provided to prevent fluctuations in the power supply to the primary winding of the transformer and another DC stabilized power source circuit and another inverter are also provided to prevent fluctuations in the power supply to the primary winding of the side-voltage transformer, regardless of fluctuations of the source voltage.
As described above, the conventional X-ray diagnostic apparatus of the pre-ignition type is provided with two DC stabilized power source circuits and two inverters to cope with fluctuations in the power supply. This results in a complicated structure and high manufacturing costs; thus there is room for improvement.